Portable, free standing fans of various sizes have been used for many years. The normal use of a portable fan is to provide a cooling sensation to the body of the user. This is accomplished by the current of air generated by the fan passing over the skin of an individual. The current of air that passes over an individual serves to increase the convective heat loss of the body through the natural evaporative process of moisture (e.g. sweat) on the skin. The greater the amount of evaporation the greater the sensation of cooling. Further, the greater the portion of the body that can be effected by the current of air the greater the cooling sensation to the user.
Conventional portable fans using axial impellers have been utilized to achieve these desired cooling effects. However conventional axial impeller have several disadvantages. The axial impeller is normally large and requires even larger protective grills. These types of devices not only produce an air stream but may also produce a significant volume of air movement. The shape of the air stream produced by the conventional portable fan utilizing an axial impeller is conical. As the air stream travels away from the fan the area of coverage grows in diameter. The significant volume of air combined with the growth in the coverage area of the air stream may cause objects, (such as papers for example) to be dislodged from their intended place. Further, the volume and growth of the coverage area as described increases the possibility that dust, pollen, dander, etc. will be disturbed and induced to become airborne. Airborne dust and debris can be detrimental to, for example, respiratory conditions.
The volume of air produced by a conventional fan utilizing an axial impeller also requires a predetermined amount of power to produce the volume of air. A greater volume of air requires more power from the electric motor of the fan. More power from the electric motor normally requires that the motor utilize more materials such as lamination steel and copper wire. The increased material usage increases the cost of the conventional fan for both the manufacturer and the end user.
The volume of air produced by a conventional portable fan using an axial impeller also may contribute to increased thrust. Increased thrust is detrimental to the stability of the fan. This thrust must be counteracted by utilizing a large base to stabilize the device. The thrust and stability problem can be exacerbated if the device is elevated above its support surface. The large components (blades and protective grills) of axial fans along with the increased thrust and corresponding stability problems do not allow these types of devices to be easily transportable (portable) or to have space saving characteristics.
The large base and grills of the conventional portable fan, as described, require a significant amount of packaging material as well as space for shipment. In an effort to conserve space requirements for shipping these fans are often disassembled and require customer assembly. If the customer fails to follow the assembly instructions properly the fan may not be stable, safe and/or may be returned to the manufacturer. This may causes extra cost for the manufacturer, retailer and be the cause of a poor customer experience.